I. Field
The present disclosure relates generally to the art of telecommunications, and more specifically to accurate phase and amplitude tracking in newer low frequency WiFi environments.
II. Background
The 802.11 WiFi standard enables the implementation of wireless local area networks. Newer 802.11 standards have been discussed that will operate with increased speed, increased bandwidth, and are projected to enable operation in various frequency bands. Different versions of 802.11 have been proposed, including 802.11ac, 802.11ad, 802.11af, and 802.11ah. Each of these versions offers different benefits, but in certain instances, operation according to these protocols presents certain challenges.
As an example, transmission at frequencies below 1 GHz enables communications over a longer range. In such a low frequency scenario, throughput is not relatively high, and in some instances 100 kbps may be encountered. The issue with such an arrangement is that the transmission bandwidth tends to be very low, and data transmitted using previous 802.11 protocols simply is not transmittable fast enough. Certain proposals have been suggested to deal with this situation, including altering the pilot signal to occur at various points during a transmitted frame, changing between frequencies, known as employing a “walking pilot.”
When the pilot and other transmitted signals vary during a frame, the receiver can have difficulty discerning both the pilot signal and the other transmitted signals in that there can be uncertainty about the data received, particularly due to Doppler effects. As a result, estimating phase and amplitude of the received signal can be difficult, as phase and amplitude of the received signal may deviate from an expected value due to the associated uncertainties. Further, power distribution can vary in the frequency domain because of the analog and digital front end filters and the channel variances.
It would therefore be beneficial to provide a system that can more accurately track signal phase and amplitude in signals that vary in the frequency domain.